Since it is considered that antimicrobial peptides have broad antimicrobial spectra and hardly generate drug-resistant microorganisms, use of antimicrobial peptides is expected for the purpose of preventing and treating bacterial infectious diseases of human and animals or of adding antimicrobial property to food materials and the like articles.
A large number of antimicrobial peptides have so far been isolated from animals and plants. For example, an antimicrobial peptide derived from a Taiwanese beetle and an antimicrobial agent containing said antimicrobial peptide as the active ingredient have been disclosed (cf. Reference 1). Also, an antimicrobial peptide derived from scorpion toxin and an antimicrobial agent containing said antimicrobial peptide as the active ingredient have bee disclosed (e.g., see Reference 2).
Each of the aforementioned antimicrobial peptides contains lysine, arginine and/or histidine and the like basic amino acids and is called cationic antimicrobial peptide in which its charge as the entire peptide molecule becomes positive. It is considered that the reaction principle of these antimicrobial peptides is based on the electrostatic interaction of the positively charged basic amino acid moiety in the antimicrobial peptide with the cell surface membrane (e.g., see Reference 3).
Each of the aforementioned antimicrobial peptides described in the respective official gazettes is a result of discovering and isolating a substance originally existing as an antimicrobial peptide in the natural world (or a peptide prepared by partially modifying the amino acid sequence of a natural antimicrobial peptide). Thus, so far as a peptide originally existing as an antimicrobial peptide is used as the main component, it is difficult in general to develop an antimicrobial agent having the antimicrobial performance superior to the antimicrobial activity and antimicrobial spectrum originally exerted by the peptide in the natural world.
Reference 1 JP-A-2000-063400 official gazette
Reference 2 JP-A-2001-186887 official gazette
Reference 3 M. Zasloff. Nature, vol. 415. pp. 389–395, 2002